Re: Final Phase I SiPM array report

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Fri, 21 Dec 2007, George Lolos wrote:

Dear George et al.,

nice report. As I went through I found a couple of information which is
missing and would be really nice to include in the report.
I give the list below.

Cheers and a Happy 2008
Elke

1. Page 2:
   it would be nice to have a sketch of the setup. This should include
   for example the length of the BCF-20 fiber and exact wavelength used
   for the laser and details like that.

2. if you illuminate one individual 3x3mm^2 cell in the array you say
   there is no cross talk to the other cells.
   I totally agree the illumination is very concentrated on one cell but
   we have currently no means to measure the cross talk on the PCB between
   cells. I think this would actually be a very interesting information.

3. figure 2
   the measurements for G3 become less dense after 27.7 V is this a
   plotting artifact? For G4 some of the points look to be measured twice
   but give different Current for both measurements.

4. do we have noise spectra from the individual arrays

5. what was the voltage for characterizing the maximum signal size.
   Are we sure the electronics boards for the arrays have all the same
   amplification factor.

6. Figure 6,7,8
   have been obtained by illuminating each cell and than plotting the
   results from the individual measurements in one plot.
   What are the maximum variations coming from instabilities of the
   laser. Has each cell an individual amplifier channel and the summing of
   all cells happens afterwords or are the cells summed before and than
   amplified. Do we have an electronic diagram of the SiPMT arrays.

7. page 7
   It would be nice to specify in a bit more detail what a bundle of
   BCF-20 fibers means, like number of fibers, length, .....

8. figure 10
   It is not completely clear the scope shot is after all noise problems
   with the power supply have been fixed or not.
   As G6 is one of the arrays showing the strange behavior in the I-V
   curves could the noise in the spectra not results from this.
   Carl also saw this strange noise with increasing breakdown voltage.

9. I would suggest to use power supplies like the ones from eutron or the
   caen A515 LV which has 0-100V and max 200microA, the ripple is 3 mV P-P
   we used them for our HERMES silicon detectors and the DESY people use
   them now for their SiPMTs. And in general it is a good idea to filter
   directly in front of a Silicon detector with an R-C circuit.

10. Do you have a plot like Fig 10 for G6 after the board was exchanged.
    In general it would be nice to state more clearly which measurements
    have been done with an electronics board connected and if which one.

11. what is Sensl saying is the relevance of this reverse biasing of a
    silicon. Are we supposed to learn something about the doping.
    Because now the current should depend on the carriers as there is no
    depletion area anymore.
    I have a hard time to understand what the operation of a diode tells
    me about the operation of a SiPMT.

12. page 14
    I would give the link of the wiki-page just to be complete.

13. page 15
    I think it is critical to measure the gain variation on the
    several 3x3mm^2 samples we have. Carl, could you please make this a
    priority.
    In principal a mounting solution was already a Phase I deliverable.
    There are some other things in the Phase I SoW like back thinning
    which have not been done yet. But that is our not our biggest problem.




> Date: Fri, 21 Dec 2007 18:35:29 -0600
> From: George Lolos <George.Lolos@uregina.ca>
> To: halld-cal@jlab.org
> Subject: Final Phase I SiPM array report
>
> Dear calorimetereans:
>
> I have posted the final version of the Phase I close-out report as GlueX-doc-926-v3.  Ho Ho Ho!
>
> Merry Christmas and a Happy New Year and easy on the liquid nourishment and the sweet stuff....
>
> George
>
>
>

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